Refining nickel matte and nickel-copper matte



No Drawing. I

Patented Sept. 1.4, 1926.

UNITED STATES 1,599,424 PATENT OFFICE.

OTTO LELLEP, OF EGYPT, PENNSYLVANIA, ASSIGNORTO THE INTERNATIONAL NICKELOF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

NICKEL MATTE AND NICKEL-COPPER MATTE.

The object of my invention is to provide an improved method ofeliminating sulphur .from nickel matte or'nickel-copper matte, or moltennickel-copper alloy or nickel, by blowing through the molten bath orover the molten bath a hot gas or mixture of My method provides for theformation ofmetal oxide in the molten bath and for the accurate'controlof such formation for assisting in the elimination of sulphur present inthe bath-either as sulphide or as sulphur dioxide.

My invention further provides for the reduction of metal oxide either ofnickel or of copper, in the molten bath, when such oxide has been formedin the process of eliminating sulphur.

My method provides for a repeated alternation of the condition of themolten bath, first oxidizing it to the saturation point for the oxideand then reducing it till free of oxide. In this way my process achievesthe elimination of sulphur content down to any point required incommercial nickel or copper-nickel alloy.

In carrying out my process it is necessary to produce and maintain atemperature in the bath of metal not lower than the melting point ofMonel metal or 1380.C., the maximum temperature may be 17 C. but atemperature of about 1500 C. for nickelcopper and 1600 C. for nickel ispreferable.

This temperature may be produced and maintained by any suitablemethod-such'as heating up a converter charged with cold matte or moltenmatte by means of a blast composed of a mixture of air and a suitablefuel in about theoretical proportions; or by heating up a reverberatoryfurnace'charged with cold matte or with molten matte from a converter orany other source and acting control of temperature of the bath and theApplication filed April 7,

nickel matte or i 1923. Serial No. 630,618.

modified converter like that used in the concentration of copper-nickelmatte. The other type of apparatus is a low arch reverberatory furnace,preferably of the regeu erative-type. The choice of apparatus 'used 1ncarrying out my invention depends on local conditions, such-as kind offuel available and its cost. To carry out the process in the converterheat must be provided to raise the converter temperature and to maintainit at preferably about 1500 C. for

Monel metal and 1600 C. for nickel. For this purpose, during the laststage of converting beginning with the moment when the matte issufficiently refined from iron, I mix with the air blast a suitableamount of a fuel which may be gaseous, liquid, or

powdered such as natural gas, blue water gas, kerosene or oil vapor, orany suitable liquid fuel preferably atomized, or any suitable powderedfuel such as powdered coal, charcoal or coke. It is highly desirablethat the fuel be intimately mixed with the air. Such a mixture when itstrikes the liquid metal whichis already at a high-temperature burnsalmost instantaneously and supplies the necessary additional heat.

To introduce gaseous fuelinto the blast the pipe supplying the tuyeresmay be provided with a mixing T with suitable connections for air andgas or each individual tuyere may be provided with a gas supply. Tointroduceliquid fuel into'the blast this fuel may be transformed into aVaporand may then be introduced in the same way as a gas. In case theliquid fuel such as fuel oil does not vaporize completely withoutleaving a carbonaceous residue, this fuel may be.sprayed through asuitable atomiz-' ing or spraying nozzle into the air blast, thetemperature of which has previously been raisedto a point below theignition point of the fuel. In this way it'is possible to transform evenheavier hydrocarbons into a fine mist suspended in the air. The liquidfuel may be sprayed through a suitable pipe or nozzle into the commonair supply pipe or into each individual tuyere.

' "Powdered fuel mayx be introduced by any.

suitable meansinto the blast.

In any case means should'be provided tb supply through the tuyeres ascomplete and fine a mixture of fuel and air as is possible,

" to insure a practically instantaneous com- 'jl 'lbustion. as soon asthe mixtureleaves the i comparatively against the white hot metal.

and strikes I To prevent the mixture from back-firing the tuyeres cooltuyere should be kept comparatively cool either by .air or water coolingand the velocity of the fuel and air mixture should be above thevelocity of flame propagation. To obtain an air cooling effect on thetuyre body, this body may be provided with a number of ribs or flangesto. conduct and radiate the heat to the air, and may be made of a. heavcasting projecting through the converter shell about half way into theconverter lining. Similar tuyeres or burners are used in some gasfurnaces which burn homogeneous mixtures of gas'and air. Usual cleaningand observation holes should be provided to enable a punching of thetuyere when necessary.

or the usual matte concentration converter may be equipped with a blastof fuel mixed with air. In case solid c'old pigs of refined matte arecharged into the fuel heated converter the cold matte will first'bemolten down by the burning blast and then the tem- .perature of. theliquid matte is raised.

Vvhether the same converter is used or a'second converter, the procedureis the same.

At the beginning, the amount of fuel is regulated to approximately thetheoretical proportion as this proportion gives the highest flametemperature and heats up the matte most quickly. When the temperature ishigh enough so that no excessive free oxides are floating on the metal,a percentage of excess air may be provided by diminishing the flow offuel. A lean flame has a stronger oxidizing effect and eliminatessulphur faster than a theoretical flame. The proportion of excess air,whenthe coverter has been heated up, may go as high as and stillmaintain a temperature of 1500 C; because this excess air burns with thecombined sulphur of the matte and this supplies a part of the heat. Thesulphur is eliminated in this way rapidly until the metal analyses about0.5% sulphur. To free the metal from this last trace of sulphur specialmeasures must be taken as this sulphur seems to adhere to the. nickelwith a particular tenac- If a large excess of air be blown into ity. thebath the metal will oxidize rapidly and as the metal oxide is infusibleat thls temperature, solid' crusts of metal oxide form on duced to about0.5%, the blast should be made either neutral or reducing. It isprobable that this last trace of sulphur in the metal is in the form ofdissolved sulphur dioxide which may be washed out by any gas in contactwith the metal. A neutral or reducing flame blown through the tuyeresinto the bath has this washing effect on the sulphur without overoxidizing the metal and at the same time maintaining the necessary hightemperature of 1500 (3., or 1600 C. Instead of a steady neutral flamethe bath maybe blown alternately, first with a slightly reducing flameuntil all the oxide is reduced to-metal, and then with a sligthlyoxidizing flame until all the metal is saturated with dissolved oxide.Continued alternation of reducing and oxidizing flame will finally freethe bath from sulphur within the commercial limits found in Monel metaland nickel, The final trace of sulphur (below 0.5%) may be removed alittle more quickly by, alternate short blasts of reducing-and oxidizingflame than by a steady neutral blast. l5yselect-in a suitabletemperature and character of blast the metal may be brought to anydesired pitch.

' Instead of supplying the fuel and air blast together and carryingout'the combustion of the fuel in the metal bath, the fuel may be burnedinside the converter but on top of the. metals The second type ofapparatus in which the direct desulphurization of nickel or Monel metalmatte maybe carried out is a low arch reverberatory furnace. The arch ofthe furnace is built preferably low so that it may be close to thesurface of the metal to obtain a strong rubbing action of the oxidizingflame on the matte. The usual construction of the curved arch above thehearth, or

the laboratory of the furnace makes the distance between the levelsurface of the metal and the curved roof of the furnace greater in thecenter and less at the sides. To distribute the. 'fire gases evenlyabove the entire surface *of the metal and bring the gases into closestcontact with the metal any type of socalled flat arch is recommended inwhich the refractory material of the roof is suspended from an suitableconstruction and forms a flat roof parallel to the level of metalsurface. The depth of the metal in the hearth is kept shallow to exposea maximum surface per minimum of metal weight.

The furnace is built preferably of the reslightly oxidizing flame. Thena strongly oxidizing flame is applied to remove the bulk of the sulphurquickly. The same washing out? method to remove the last traces ofsulphur (below 0.5%) may beapplied in the reverberatory furnace as wasdescribed for the converter. Furthermore it is desirable to stir up themetal and thus renew the surface of metal exposed to the refining actionof the gases. For thispurpose a pole may be inserted into the bath suchas is used in the refining of copper, or the hearth ma be provided withtuyeres through whlch a gas may be blown into the bath of metal.

In comparison, the fuel consumption of the reverberatory regenerativefurnace for this' process is much more economical than the fuelconsumption of the converter. The main heat loss in the converterprocess is the considerable amount of heat in the waste gases escapingat 1500 C. to 1600 C. In the regenerative furnace vthe fire gases escapeat a temperature of about 350 C.

. Having thus fully described my process, I claim:

1. In the process of eliminating sulphur from nickel matte ornickel-copper matte or metal, the steps consisting of treating the samein the molten state with a blast of air, and supplying additional heatto the reaction.

.met-al, the steps consisting of treatingthe 2. The method ofeliminating sulphur below 1% from nickel or nickel-copper alloy in whichthe molten metal at a temperature between 1380? O: and 17 50 C. is actedupon by a gas blast, said gas blast being alternately and periodicallyoxidizing and reducing in character.

3. In the process of eliminating sulphur from nickel matte ornickel-copper matte or same in the molten state with a gaseous ast, andsimultaneously burning combustible material in such relation as tosupply further heat units to the operation.

4. In the process of elimlnating sulphur from nickel matte ornickel-copper matte or metal, the step consisting of treating the samein the molten state with a blast containing a mixture of air and fuel.

5. In the process of eliminating sulphur. from nickel matte ornickel-copper matte or metal, the steps consisting of treating the .samein the molten state wlth a gaseous blast of an oxidizing character, andthereafter treating 'the same with a gaseous blast of substantiallynon-oxidizing character;

6. In'the process of eliminating sulphur from nickel matte ornickel-copper matte or metal, the steps consisting of treating thematerial in the molten state with a mixture of air-and fuel of anoxidizing character, and then treating the same with a mixture of airand fuel of a non-oxidizing character.-

7. In the converting of nickel-containing matte, the steps consisting inoxidizing the sulphur while the matte is molten, and keeping thetemperature above 1380 C. by supa to the reaction.

plying additional heat OTTO LELLEP.

